Efficiency of solid state Photomultipliers in photon number resolution

Solid State Photomultipliers (SSPM) are widely recognized as new generation of photodetectors competitive with APD and PMT in various applications. SSPM advantages are high gain and ultra-low excess noise factor of internal amplification resulting in ability to detect single photons, high photon detection efficiency, fast response and good time resolution. SSPM drawbacks are high dark count rate, high probability of cross-talk and afterpulsing, and low dynamic range. Many applications in Nuclear Science and Medical Imaging for photodetector with scintillator require good energy resolution, which is represented with respect to photodetector itself by pulse height resolution or so-called Photon Number Resolution (PNR). The purpose of this study is to express SSPM PNR in analytical form taking into account excess noise factor of crosstalk and afterpulsing as well as nonlinearity of photoresponse due to limited number of pixels and finite reset time. Normalization of PNR relatively to ideal detector characterizes the intrinsic detector performance in terms of total excess noise factor of photodetection or, inversely, in terms of detective quantum efficiency, which seems to be very powerful tool for SSPM optimization and evaluation of SSPM applicability and competitiveness.